Effects of the Ingredients on Maturity and Humification during Kitchen Waste Composting as Illustrated by Nuclear Magnetic Resonance

Kitchen waste (KW) production has risen considerably due to the increasing affluence of populations and a booming catering sector. If not properly disposed, KW can bring serious issues for the environment. Composting is widely used as an efficient method for the resource utilization of KW. In the present paper, the effects of different ratios of ingredients (corn straw: garden waste = 4:1, based on the dry mass) on maturity and humification during KW composting were investigated. The results showed that the nitrogen retention capacity of the treatments with a ratio of ingredients to KW of 1:2.5 and 1:5.0 was higher than that of other treatments. Additionally, it was found that the number of ingredients had an effect on the germination index (GI) during composting, and the final GI values of the four treatments were in the following order: 1:7.5 > 1:5.0 > 1:10.0 > 1:2.5. Nuclear magnetic resonance (NMR) showed that the organic matter (OM) content of each treatment increased after composting, and the maturity of the 1:2.5 and 1:5.0 treatments was higher than the other two treatments. Redundancy analysis (RDA) showed that the maturity and humification were correlated with moisture content, pH and NO3--N during composting. This study concludes that the treatment with an ingredients to KW ratio of 1:5.0 was much more useful for KW composting, which is of importance to guide the disposal of KW.